These rocks are also known as ultramafic rocks.
Ultramafic Rock:
See Ultrabasic Rock.
Unconformity:
A contact between two rock units of significantly different ages. An unconformity is a gap in the time record for that location.
mafic -- Term used to describe the amount of dark-colored iron and magnesium minerals in an igneous rock. Complement of felsic.
Mafic Magma, Magma, Magma Plume, Magnitude, Mantle, Marble, Mass Wasting, Metamorphic Rock, Metamorphism, Metasomatic Metamorphism, Mica, Mid-Oceanic Ridge, Mineral, Monocline, Mudstone, ...
mafic Referring to a generally dark-colored igneous rock with significant amounts of one or more ferromagnesian minerals, or to a magma with significant amounts of iron and magnesium.
Evidence favoring some early non-mafic crustal rocks is found in the discovery of the mineral Zircon (a gemstone), ZrSiO4, at various localities, mainly Australia, ...
It separates the deeper, mafic igneous rock of the Central Pacific Basin from the partially submerged continental areas of felsic igneous rock on its margins.
The cause of the Moho is thought to be a change in rock composition from rocks containing plagioclase feldspar (above) to rocks that contain none (below). The second event is a chemical discontinuity between ultramafic cumulates and tectonized ...
 See also: Area, Surface, Sediment, Crust, Region
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